I want to install Ubuntu to a 4Gb USB stick, so that I can boot it on other computers, but I heard that a persistent file system never deletes data and so just fills up. This would be a problem as I like to keep Ubuntu up to date, and downloading 100Mb worth of upgrades on a regular basis would fill up the drive quite fast if they never truly overwrote old ones.

So can someone please tell me if this is true and, also, if there are any advantages to using a persistent file system over just installing Ubuntu to the drive.

In addition, would it be possible to install the Ubuntu installer onto a normal installation of Ubuntu - ie, if I used the installer to install to the live stick, would I be able to get the installer back on the USB stick to install it on further machines? It's not really an issue if I can't, but I am curious. Thank you.

2 Answers
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I think the persistent file system only doesn't delete data that already exists in the SquashFS file, ie. what's already there by default. So if you try to uninstall, say, Firefox, then you won't get space. However, if you install a new program, like Pidgin, and then later uninstall Pidgin, then you will free up your space.

So if you're only going to install and not going to remove what you've already installed, then persistence is the best option is to use a persistent file system, because if you do a full install then it'll take up more space.
Full install takes up more space because when you do an install then it uncompresses what was in the (highly compressed) SquashFS filesystem.

If there are some programs in the default ISO that you are not going to use, then I suggest you use UCK (Ubuntu Customization Kit), which lets you customize the Ubuntu ISO, to remove those programs and maybe install/update any programs you want to use. That way all those changes will be in the SquashFS filesystem as well, so everything will be compressed and you'll have more free space left at the end of it.

This is what I have been doing for some time now and it's been working nicely.

I find persistent file system sticks to be slow and I much prefer just doing a full install to the stick now - but thanks for explaining how persistent file systems can still delete some data.
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Sman789Jul 14 '12 at 12:57

The advantage of having Ubuntu installed in a pen drive is that you can always carry your OS & files with you no matter where you go and can use it in every machine. The disadvantage is, as you already said, a pen drive have a relatively small capacity and will fill up pretty easily.

If you want that kind of portability the pen drive gives to you, I suggest you consider buying a pen drive with more capacity (I saw there are some up to 64gb!). Some guys were discussing the same question in here: FULL install Ubuntu on 4GB USB drive

I didn't understand what you meant with the last question, but you can partition your external disc (pen drive) and in the first partition install the installer and in the second one the actual installation of Ubuntu. Personally I haven't tried this, but I think this thread will help you.

I didn't mean the advantage of installing to a USB stick - I already know that's what I'm going to do. I meant, is it better to install it using the USB creator and use a persistant file system, or to use the Ubuntu installer to actually install the full OS to the stick? My second question was: if I chose the second option, and wanted to do a full install (not persistant) to the USB stick, would I actually be able to do it from a normal install of ubuntu or would I have to get a second stick, install the live image to that, and then use that to do a full install to the first stick?
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Sman789May 13 '12 at 20:53